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Postby s.freeman66 » Mon Mar 31, 2008 11:12 pm

We are putting a seperate consumer unit in our garage, we have put a 10mm cable from where the house consumer unit is to the garage consumer unit.
We will connect the cable to a 40amp fuse in our consumer unit
Then in the garage we have wiring in place for a lighting circuit (1.5MM) to a 5 amp fuse, ring main(2.5mm)to a 16 or 32amp fuse(which is correct)shower(10mm)to a 40 amp fuse and compressor(6mm) to a 32amp fuse.
Just want to check we have everything in place ready for when we get a electrician in to connect everything up. (Little way off that yet but once floors and ceiling up and down don't want to have to add condue if we have it wrong)

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Postby ericmark » Tue Apr 01, 2008 12:52 am

If I am reading correct.
1 x 40 Amp MCB feeding 40 amp MCB plus a load of others?
You need some rethink if thats the case. You will never want a MCB in the garage the same size as the one supplying it.
All needs calculating you are allowed 3% volt drop on lights so 10mm cable with 40 amp breaker max length at 4.4mV/A/m = 40 meters
Then also ELI etc.
If you are going to design then you must look at all aspects including if your qualifications will allow you to sign the installation certificate.
A good starting point is to follow links to projects and Part P and down load the document. I don't want to put you off but it may need some qualifications to sign the design and installation part of the certificate and although in theory you can sign for two and the electrician only signs for inspection and testing many will not because they are members of systems which don't allow that flexibility.
Also be aware that on the 1st July 2008 new regulations come into force. Once these are in force everything will need RCD protection at the moment it is only required where showers and baths are used or where things outside may be plugged in. The new regs will also affect your shower no longer are the rules different for shower in bedroom to shower in bathroom and zone 3 will go and the 2.5 meters to nearest socket is increased to 3 meters.
I don't see any mention of RCD's I assume over site.
also note new types of consumer units now being used to comply with 17th Edition and remember you may need to change house consumer unit as well if after 1st July.

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